This invention is directed to the field of downwell hydrocarbon production, such as oil and gas, more particularly to the use of high energy ultrasonics, as the means to stimulate the hydrocarbon containing strata surrounding a well casing for its eventual recovery.
The present invention relates to a system, preferably in the form of a method, to stimulate hydrocarbon flow from wells whose production has been reduced to marginal or entirely unfeasible. The recognition that such wells may still contain a significant pool of oil, for example, has prompted many in the oil industry to investigate economical ways to stimulate production from such wells. A typical correction for such a well is to apply a fracture, also called a xe2x80x9cfrac. xe2x80x9d A frac consists of introducing a foreign substance, such as water, steam or inert gas to the well casing under pressure. The pressurized gas or liquid exits the casing through the perforations and actually breaks up obstructions to the flow of hydrocarbons and affects the geological formation in the vicinity of the well. When the frac pressure is released, the well must be cleaned, usually by swabbing, and the foreign substance is pumped out or removed under natural pressure for disposal. When the well has stabilized, an increased flow of liquid and gas from the well can result.
The prior art, as reflected in the following U.S. Patents, has offered a number of different approaches to the conventional frac method:
a.) U.S. Pat. No. 5,836,389, to Wagner et al., teaches an oil recovery system utilizing an impulse wave device to produce impulse waves which travel down-hole and strike a bridge plug. When the impulse waves strike the bridge plug, weak elastic waves are created. After creation, the weak elastic waves propagate in all directions. The weak elastic waves are maintained in a general area near an oil formation by a conventional packer and a diffuser/deflector.
b.) U.S. Pat. No. 5,826,653, to Rynne et al., is directed to a method which employs multiple sources of acoustical power in an array about and spaced-apart from the surface, and directing a volume of acoustical excitation from the sources into the region containing the material to be recovered.
c.) U.S. Pat. No. 4,537,256, to Beard, relates to a sonic fracing process that uses sonic waves to crack and loosen the interstices of the oil and gas formation.
d.) U.S. Pat. No. 4,437,518, to Williams, teaches a recovery system that uses an excitation apparatus lowered through the casing of an oil well until it is submerged in oil. The apparatus includes a gas discharge tube which emits radiation, either ultraviolet or infra-red, into the surrounding oil. Next, another section of the excitation apparatus provides a mechanical energy input to the oil. The effect is to increase the pressure within the well and to cause the oil to flow more freely, thereby markedly increasing the productivity of the well after the treatment has been completed.
e.) U.S. Pat. No. 4,417,621, to Medlin et al., is directed to a method for recovering oil from a subterranean, viscous oil-containing formation by injecting a gaseous driving fluid such as carbon dioxide into the formation and recovering oil therefrom while simultaneously transmitting vibrations in the seismic frequency range having an amplitude not exceeding 100 Angstrom units through the formation which enhances the flow of the carbon dioxide and thereby increases the efficiency of recovering the oil.
f) U.S. Pat. No. 4,343,356, to Riggs et al., relates to a system for the stimulation of fluid flow from a sub surface formation by the creation of a plasma region, or shock wave such as by electrical discharge, to ionize and gasify the material for recovery.
While the above prior art offers different approaches to the achieving improved well production, only U.S. Pat. No. 5,595,243, to Maki, Jr. et al., suggests the use of transducers as a means to stimulate by the use of ultrasonic waves. This patent discloses a method and apparatus for cleaning the wellbore and the near wellbore region. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged around the sonde. Electrical power provided by a cable is converted to acoustic energy. The high intensity acoustic energy directed to the borehole wall and into the near wellbore region, redissolves or resuspends the material which is reducing the permeability of the formation and/or restricting flow in the wellbore.
The present invention differs from the prior arts procedures described above by the provision of a high powered, ultrasonic system for stimulating the flow of hydrocarbon products, such as gas and oil, from low or non producing wells, where the system hereof is ecologically friendly. The manner by which the present invention achieves these goals will become apparent from the following description, particularly when read in conjunction with the accompanying drawings.
The invention relates to a system for stimulating hydrocarbon production, such as from low producing wells, including a unique means to effect the stimulation. The process of the system comprises the steps of lowering a high powered, tuned transducer assembly down a well casing about which stimulation of the surrounding strata is desired. As the transducer assembly reaches the desired depth, the assembly is energized to cause sonic waves to extend laterally therefrom omni-directionally in a very narrow beam focused on the horizontal direction. The excitation causes three simultaneous effects: liquid degassing, cavitation, and breaking of cohesion bonds. The combined effect is to release the hydrocarbon, such as oil and/or gas, and effect a normal or enhanced flow from the well. The process has ecological benefits as no foreign substances need to be added to the well, and since the sonic waves pass unimpeded through the well casing, the process may be used with old wells that have deteriorated over the years, which would otherwise be damaged by conventional fracing procedures.
The transducer assembly is a sealed housing containing a plurality of aligned, cylindrical, piezoelectric members, spaced apart by non conductive spacer elements. The respective piezoelectric members and spacer elements are encased in a high viscous oil medium, such as castor oil, where the oil medium is in communication with a pressure compensator to adjust the pressure of the oil medium with to be equal to the surrounding environment. As part of the energizing mechanism, the scaled housing includes a transformer section in electrical communication with an above ground power source. The purpose of the transformer is two fold: (a) step up the voltage on the transmission line, and (b) match the transducer impedance to the characteristic impedance of the transmission line (50xc2x1j0 xcexa9).
Accordingly, an object of this invention is the provision of an effective, ecologically friendly system to stimulate oil or gas production from low producing wells, for example.
Another object hereof is the use of a piezoelectric, transducer assembly, engineered to emit sonic waves throughout 360 degrees about the assembly, along a narrow, horizontal beam of about 2 to 3xc2x0.
These and other objects will become more apparent to those skilled in the art from the following specification.